Reduced Jacketed Bullet Bore Resistance

ABSTRACT

A jacketed structure includes at least one penetrator slug; a jacket surrounding the at least one penetrator slug; and a deformable sleeve surrounding a portion of the at least one penetrator slug and encased by the jacket. The deformable sleeve includes porous material, which absorbs plastic deflection of the jacket during an engraving process with a barrel of a weapon during firing. The at least one penetrator slug includes material having a hardness value greater than a hardness value of the jacket and the deformable sleeve. The deformable sleeve surrounds a rear portion of the at least one penetrator slug. The deformable sleeve surrounds approximately half of the at least one penetrator slug. The deformable sleeve is configured to deform symmetrically during firing of a weapon containing the jacketed structure.

GOVERNMENT INTEREST

The embodiments herein may be manufactured, used, and/or licensed by or for the United States Government without the payment of royalties thereon.

BACKGROUND Technical Field

The embodiments herein generally relate to ammunition for weapons, and more particularly to a jacketed bullet.

Description of the Related Art

When a typical bullet 10 comprising an inner penetrator slug 12 and an outer jacket 14, as shown in FIGS. 1A and 1B, is fired the bullet 10 becomes a little longer and thinner when the jacket 14 engraves with a rifled barrel. The rifling plastically deforms (i.e., compresses the bullet 10 radially causing an elongation due to the Poisson effect). The material displaced by the rifling lands must be extruded axially thus elongating the bullet 10. The work required to perform this mechanical drawing process is energy which would otherwise be available for work to accelerate the bullet 10. Commonly owned U.S. Pat. No. 9,389,052, the complete disclosure of which, in its entirety, provides bore resistance relief through the application of flutes along the outside of internal components. The invention described therein also teaches reducing bore resistance and dispersion down range.

SUMMARY

In view of the foregoing, an embodiment herein provides a jacketed structure comprising at least one penetrator slug; a jacket surrounding the at least one penetrator slug; and a deformable sleeve surrounding a portion of the at least one penetrator slug and encased by the jacket. The deformable sleeve may comprise porous material. The porous material may absorb plastic deflection of the jacket during an engraving process with a barrel of a weapon during firing. The porous material may comprise sintered material. The at least one penetrator slug may comprise material having a hardness value greater than a hardness value of the jacket and the deformable sleeve. The deformable sleeve may surround a rear portion of the at least one penetrator slug. The deformable sleeve may surround approximately half of the at least one penetrator slug. The porous material may comprise a porosity between 1% and 50%. The porous material may comprise any of Al, Cu, Fe, Ni, Mo, Ti, and Si. The deformable sleeve may be configured to deform symmetrically during firing of a weapon containing the jacketed structure.

Another embodiment provides a method comprising providing a jacketed bullet comprising an original length and configured to be inserted into a weapon, the jacketed bullet comprising at least one penetrator slug; a jacket surrounding the at least one penetrator slug; and a deformable sleeve surrounding a portion of the at least one penetrator slug and encased by the jacket; and configuring the deformable sleeve to deform during firing of the weapon, wherein the deformation of the deformable sleeve absorbs a deformation energy exerted on the jacket thereby retaining the original length of the jacketed bullet during the firing. The method may further comprise configuring the deformable sleeve to comprise porous material. The method may further comprise configuring the porous material to absorb a plastic deflection of the jacket during an engraving process with a barrel of the weapon during the firing. The method may further comprise configuring the porous material to comprise sintered material. The method may further comprise configuring the at least one penetrator slug to comprise material having a hardness value greater than a hardness value of the jacket and the deformable sleeve. The method may further comprise configuring the deformable sleeve to surround a rear portion of the at least one penetrator slug. The method may further comprise configuring the deformable sleeve to surround approximately half of the at least one penetrator slug from a rear portion of the at least one penetrator slug up to a region or closer to where the jacket first encounters rifling lands of the weapon. The method may further comprise configuring the porous material to comprise a porosity between 1% and 50%. The method may further comprise configuring the porous material to comprise any of Al, Cu, Fe, Ni, Mo, Ti, and Si. The method may further comprise configuring the deformable sleeve to deform symmetrically during firing of the weapon containing the jacketed bullet.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:

FIG. 1A illustrates a cross-sectional side view of a conventional full metal jacket bullet;

FIG. 1B illustrates a cross-sectional end view of the conventional full metal jacket bullet cut along line A-A of FIG. 1A;

FIG. 2A illustrates a cross-sectional side view of a full metal jacket bullet according to the embodiments herein;

FIG. 2B illustrates a cross-sectional end view of the full metal jacket bullet cut along line B-B of FIG. 2A according to the embodiments herein;

FIG. 2C illustrates a cross-sectional side view of the full metal jacket bullet of FIG. 2A inside a weapon according to the embodiments herein;

FIG. 3 illustrates a cross-sectional magnified view of a portion of the deformable sleeve of the full metal jacket bullet of FIG. 2 according to the embodiments herein;

FIG. 4 illustrates a cross-sectional exploded side view of the full metal jacket bullet of FIG. 2A according to the embodiments herein;

FIG. 5A illustrates a cross-sectional side view of a full metal jacket bullet after deformation according to the embodiments herein;

FIG. 5B illustrates a cross-sectional end view of the full metal jacket bullet after deformation cut along line C-C of FIG. 5A according to the embodiments herein;

FIG. 5C illustrates a cross-sectional side view of the full metal jacket bullet of FIG. 5A inside a weapon according to the embodiments herein;

FIG. 6 is a graphical illustration of interior ballistic calculations showing reduced bore resistance effects on performance according to the embodiments herein; and

FIG. 7 is a flow diagram illustrating a method according to an embodiment herein.

DETAILED DESCRIPTION

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The embodiments herein provide a jacketed bullet comprised of internal parts one or more of which are constructed of porous materials, which provides relief during the engraving process to reduce bore resistance. During the engraving process the porous material deforms or collapses upon itself thus providing relief for the jacket material to plastically flow into. The reduction in work is realized as a reduced bore resistance which is translated into an increase in muzzle velocity. The jacketed bullet provided by the embodiments herein does not require indexing between the flutes and the barrel rifling, and enables a more uniform collapse of the relief material. Elimination of this indexing issue eliminates complex geometries and manufacturing methods for producing the bullet. Referring now to the drawings, and more particularly to FIGS. 2A through 7, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

FIGS. 2A and 2B illustrate a jacketed bullet 20 having a hard penetrator slug 22 comprising one or more core parts, and an outer jacket 24. A deformable sleeve 26 is configured between the jacket 24 and the internal core or core parts 22, wherein the sleeve 26 comprises a porous material 30 (shown in FIG. 3). The sleeve covers approximately half of the penetrator slug 22, and generally the rear portion 21 of the penetrator slug 22. The porous material 30 reduces bore resistance by providing special relief to the jacket 24 during engraving and down bore motion. The porous material 30 may include a sintered or otherwise fabricated metal comprising any of Al, Cu, Fe, Ni, Mo, Ti, Si or other material that when manufactured provides a porosity of between approximately 1% and 50%. The porous material 30 may further include various melt cast materials in which the material is cast with a crystal salt, which is then dissolved and removed after solidification. These exemplary material types have variable densities and strengths which enables an optimal configuration of the bullet 20 and programmable bore resistance.

Additionally, the mechanical properties of the porous material 30 are less than that of the material at 100% theoretical maximum density or manufactured as a non-porous solid. The penetrator slug 22 may comprise materials such as metals or ceramics, which are harder than that of the material of the jacket 24, which may comprise Cu, as well as the porous material 30 of the sleeve 26.

FIG. 2C, with reference to FIGS. 2A and 2B, illustrates the jacketed bullet 20 inside of a weapon 35 (in the drawings, the weapon/barrel are both denoted as element 35 for ease of illustration). In operation, as the bullet 20 engraves the bore 36 comprising lands 37, the jacket 24 plastically deforms into the porous interfacial material 30 of the sleeve 26 with less work than that experienced by a jacket deforming only into the center core material (as in the case of the conventional bullet 10 of FIGS. 1A and 1B). This is because the work from the plastic deformation of the jacket 24 collapses the porous material 30 of the sleeve 26 upon itself where the porous material 30 of the sleeve 26 provides a mechanical deformation relief to the plastic deformation of the jacket 24. The work required to deform the porous material 30 of the sleeve 26 is less than that required to deform the hard, inner components (e.g., penetrator slug 22) of the bullet 20 without the porous material 30 of the sleeve 26 and/or that of shearing the bullet jacket 24 longitudinally to displace the material of the jacket 24. This work reduction reduces the contact resistance experienced by the bullet 20 and thereby reduces the bore resistance during engraving and subsequent travel of the bullet 20 down bore until it reaches the muzzle of the weapon 35. Reduction in bore resistance leads to an increase in the muzzle velocity of the bullet 20. Furthermore, reducing the engraving force required enables the bullet 20 to center into the engraving region with a more concentric positioning and thus reduces dispersion downrange as opposed to a forced asymmetric engraving pattern that is experienced by a conventional hard center core bullet 10 (of FIGS. 1A and 1B). Moreover, the total energy required to deform the porous material 30 of the sleeve 26 is much less than that required to plastically deform the conventional bullet 10. Accordingly, the embodiments herein increase the muzzle velocity of the bullet 20 and reduces dispersion downrange compared with a conventional non-relieved hard core jacketed bullet 10.

The configuration of the sleeve 26 need only be sized to absorb the deformation caused during engraving process. The bullet 20 maintains its length due to the displacement being absorbed by the voids 31 (shown in FIG. 3) in the porous material 30 of the sleeve 26. FIG. 4, with reference to FIGS. 2A through 3, illustrates an exploded view of the bullet 20 with the porous deformable sleeve 26. As shown in FIG. 4, the penetrator slug 22 is configured with cut-out regions 27 to allow the sleeve 26 to wrap around the slug 22 and be planar (denoted by the dashed lines in FIG. 4) with the front portion 23 of the penetrator slug 22 in the pre-firing configuration (FIGS. 2A and 2B illustrate the bullet 20 in the pre-firing configuration).

A representation of pore collapse after engraving is presented in FIG. 5A through SC. The sleeve 26 is shown in FIGS. 5A through 5C in a reduced thickness compared with the sleeve 26 shown in FIGS. 2A and 2B. The thickness (i.e., outer diameter) of the sleeve 26 is reduced by the intrusion of the lands 37 into the jacket 24. Accordingly, the sleeve 26 is no longer planar with the front portion 23 of the penetrator slug 22.

The interior ballistic calculation results are shown graphically in FIG. 6, with reference to FIGS. 2A through 5C, and indicate that the muzzle velocity of the bullet 20 can be increased by 15 m/s for a 5.56 mm ball cartridge while keeping the peak pressure constant. This is approximately 50 ft/s. The impact is 50 ft of increased range with a possible drag coefficient of 1 ft/ft/s.

Specifically looking at a 5.56 mm M855 cartridge, as reported in the industry, the drag coefficient for a M855 bullet, is proportional to 1/velocity:

$C_{D}\alpha \frac{1}{M^{n}}\alpha \frac{1}{V^{''}}$

where n is 0.53. Therefore, if the velocity goes up from Mach 2.8 (˜927 m/s) to Mach 2.85 (˜942 m/s), then the ballistic coefficient which is inversely proportional to the drag coefficient would go up by 1.7258/1.7421 or about 1%.

Additionally, whereas the ballistic coefficient is directly proportional to the sectional density of the projectile, the change can be computed as:

$\frac{{BC}_{Cu}}{{BC}_{Mix}}\alpha \frac{\rho_{Cu}A_{t}}{{\rho_{Al}A_{Al}} + {\rho_{Cu}A_{Cu}}}$

which for a thin 50% dense aluminum sleeve of 0.089 mm wall thickness in a 5.56 mm bullet (for example, bullet 20 of FIGS. 2A and 2B) is 1.06 or about 6% lower for the composite than that of the conventional bullet (for example, bullet 10 of FIGS. 1A and 1B).

A bullet following the minimum deformation energy path will explicitly engrave more symmetrically. The deformable sleeve 26 is configured to have a thickness which absorbs the deformation from land intrusion uniformly and no more. Thus, the entire sleeve 26 will deform symmetrically. This symmetrical engraving reduces in-bore balloting and thereby reduces dispersion.

The modulus of elasticity (E) scales linearly with density of sintered alumina ranging from 40-390 GPa for ρ/ρ_(th) from 0.60 to 0.99. The behavior follows the following empirical function:

$E = {{903\left( \frac{\rho}{\rho_{th}} \right)} - 510}$

Given a bullet 20 with a solid copper core 22 having a modulus of 110 GPa, a sintered alumina sleeve 26 having a 40 GPa modulus or other porous sleeve 26 made of other materials having a modulus significantly lower than that of the copper core would provide the desired collapsing behavior.

According to the embodiments herein, only enough of the porous material 30 of the sleeve 26 is used to affect the absorption of the appropriate amount of displacement required for engraving. A thickness of 0.089 mm of the sleeve 26 is sufficient to account for the entire engraving deformation with a 50% dense material 30 sleeve 26. If the engraving deformation has the choice between an axial extrusion of the solid core 22 and the collapse of a porous part, the path of minimum energy will be taken which will be the collapse of the porous sleeve 26.

FIG. 7, with reference to FIGS. 2A through 6, is a flow diagram illustrating a method according to an embodiment herein. The method comprises providing (40) a jacketed bullet 20 comprising an original length and configured to be inserted into a weapon 35, the jacketed bullet 20 comprising at least one penetrator slug 22; a jacket 24 surrounding the at least one penetrator slug 22; and a deformable sleeve 26 surrounding a portion of the at least one penetrator slug 22 and encased by the jacket 24; and configuring (42) the deformable sleeve 26 to deform during firing of the weapon 35, wherein the deformation of the deformable sleeve 26 absorbs a deformation energy exerted on the jacket 24 thereby retaining the original length of the jacketed bullet 20 during the firing. The method may further comprise configuring the deformable sleeve 26 to comprise porous material 30. The method may further comprise configuring the porous material 30 to absorb a plastic deflection of the jacket 24 during an engraving process with a barrel of the weapon 35 during the firing. The method may further comprise configuring the porous material 30 to comprise sintered material. The method may further comprise configuring the at least one penetrator slug 22 to comprise material having a hardness value greater than a hardness value of the jacket 24 and the deformable sleeve 26. The method may further comprise configuring the deformable sleeve 26 to surround a rear portion 21 of the at least one penetrator slug 22. The method may further comprise configuring the deformable sleeve 26 to surround approximately half of the at least one penetrator slug 22 from the rear portion 21 of the at least one penetrator slug 22 up to a region or closer to where the jacket 24 first encounters rifling lands 37 of the weapon 35. The method may further comprise configuring the porous material 30 to comprise a porosity between 1% and 50%. The method may further comprise configuring the porous material 30 to comprise any of Al, Cu, Fe, Ni, Mo, Ti, and Si. The method may further comprise configuring the deformable sleeve 26 to deform symmetrically during firing of the weapon 35 containing the jacketed bullet 20.

The use of a porous material 30 for the sleeve 26 to absorb the plastic deflection of the outer jacket 24 provides a significant advancement in bullet technology. Conventional technology depends upon the hard, center components 12 of a jacketed bullet 10 and the axial shearing of the jacket 14 itself to absorb the plastic deformation work. The application and incorporation of a porous sleeve 26 as an interface between the bullet jacket 24 and a harder center core 22 to reduce the engraving and bore resistance as well as improve bullet dispersion increases bullet performance. The embodiments herein utilize the relative weakness associated with porous materials to the advantage of providing relief for the metal plastic displacement during firing of a weapon 35. Depending upon the net desired shape of the bullet 20, different manufacturing techniques may be utilized. For example, the bullet 20 may be formed by injection molded or extruded followed by a hipping process which would result in a consistent net shape. The hipped component would then be included in the bullet build process.

Every jacketed bullet containing a hard, center core and fired in a gun up to .50 cal could incorporate the configuration provided by the embodiments herein in order to improve performance. Any manufactured item, which contains of an external jacket housing, an internal stiff component, which needs to be consolidated and/or have a specific embossed exterior which is imparted during consolidation could also incorporate the configuration provided by the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims. 

What is claimed is:
 1. A jacketed structure comprising: at least one penetrator slug; a jacket surrounding said at least one penetrator slug; and a deformable sleeve surrounding a portion of said at least one penetrator slug and encased by said jacket.
 2. The jacketed structure of claim 1, wherein said deformable sleeve comprises porous material.
 3. The jacketed structure of claim 2, wherein said porous material absorbs plastic deflection of said jacket during an engraving process with a barrel of a weapon during firing.
 4. The jacketed structure of claim 2, wherein said porous material comprises sintered material.
 5. The jacketed structure of claim 1, wherein said at least one penetrator slug comprises material having a hardness value greater than a hardness value of said jacket and said deformable sleeve.
 6. The jacketed structure of claim 1, wherein said deformable sleeve surrounds a rear portion of said at least one penetrator slug.
 7. The jacketed structure of claim 1, wherein said deformable sleeve surrounds approximately half of said at least one penetrator slug.
 8. The jacketed structure of claim 2, wherein said porous material comprises a porosity between 1% and 50%.
 9. The jacketed structure of claim 2, wherein said porous material comprises any of Al, Cu, Fe, Ni, Mo, Ti, and Si.
 10. The jacketed structure of claim 1, wherein said deformable sleeve is configured to deform symmetrically during firing of a weapon containing said jacketed structure.
 11. A method comprising: providing a jacketed bullet comprising an original length and configured to be inserted into a weapon, said jacketed bullet comprising at least one penetrator slug; a jacket surrounding said at least one penetrator slug; and a deformable sleeve surrounding a portion of said at least one penetrator slug and encased by said jacket; and configuring said deformable sleeve to deform during firing of the weapon, wherein the deformation of said deformable sleeve absorbs a deformation energy exerted on said jacket thereby retaining said original length of said jacketed bullet during said firing.
 12. The method of claim 11, further comprising configuring said deformable sleeve to comprise porous material.
 13. The method of claim 12, further comprising configuring said porous material to absorb a plastic deflection of said jacket during an engraving process with a barrel of said weapon during said firing.
 14. The method of claim 12, further comprising configuring said porous material to comprise sintered material.
 15. The method of claim 11, further comprising configuring said at least one penetrator slug to comprise material having a hardness value greater than a hardness value of said jacket and said deformable sleeve.
 16. The method of claim 11, further comprising configuring said deformable sleeve to surround a rear portion of said at least one penetrator slug.
 17. The method of claim 11, further comprising configuring said deformable sleeve to surround approximately half of said at least one penetrator slug from a rear portion of said at least one penetrator slug up to a region or closer to where said jacket first encounters rifling lands of said weapon.
 18. The method of claim 12, further comprising configuring said porous material to comprise a porosity between 1% and 50%.
 19. The method of claim 12, further comprising configuring said porous material to comprise any of Al, Cu, Fe, Ni, Mo, Ti, and Si.
 20. The method of claim 11, further comprising configuring said deformable sleeve to deform symmetrically during firing of said weapon containing said jacketed bullet. 